The present invention relates to the field of computer graphics, and in particular to methods and apparatus for realistically animating water and other fluids. The present invention relates to the field of computer graphics. Many computer graphic images are created by mathematically modeling the interaction of light with a three dimensional scene from a given viewpoint. This process, called rendering, generates a two-dimensional image of the scene from the given viewpoint, and is analogous to taking a photograph of a real-world scene. Animated sequences can be created by rendering a sequence of images of a scene as the scene is gradually changed over time. A great deal of effort has been devoted to making realistic looking rendered images and animations.
Motion blur is a phenomenon resulting in the apparent streaking or blurring of rapidly moving objects. Rapidly moving objects appear to be blurred along the direction of motion relative to the viewer because of persistence of vision effects in the human visual system. Motion blur also occurs in still and motion picture photography as objects move relative to the camera during the period of exposure determined by the camera's shutter. Motion blur may be used to blur moving objects or to blur static backgrounds if the camera is moving.
In movies and photography, motion blur may be used and even exaggerated to provide a sensation of speed or motion. For these reasons, motion blur effects are often added to computer graphics and animation to make images appear as if they were conventionally photographed. Motion blur effects are typically created by evaluating the positions of all of the objects in a scene at slightly different times and then combining and rendering the results. To control the degree of motion blur, animators can specify a time interval between images that is analogous to the exposure time of a conventional camera. Previous motion blur effects apply the same amount of motion blur to all objects in an image. Additionally, the amount of motion blur remains constant over the entire animated sequence.
For improved aesthetics, it is desirable for a system and method to enable animators to vary the amount of motion blur within an image applied to different objects and to different parts of the same object. It is also desirable for animators to be able to vary the amount of motion blur over the course of an animated sequence. It is further desirable for the motion blur effect to be easily integrated within an animation system.